The present invention relates to a power converter which is capable of converting an alternating current to a direct current and inverting a direct current to an alternating, current, and more particularly to a power cut detection apparatus which detects a power cut of an alternating power source to which the power converter is connected.
When a power converter, which converts an ac (alternating current) power from a commercial power source to a dc (direct current) power to supply the dc power to loads, is constituted simply with a diode bridge, there are instances where reactive power which changes the line voltage is produced at the side of the commercial power source, or higher harmonics which cause inductive interference on communication lines such as telephone lines close to the power-transmission lines, are produced.
In order to solve such troubles, a power converter, which is so called a PWM converter, has already been put into practical use and is composed of self-quenching elements such as GTOs (gate turn-off thyristors) or transistors which are controlled on the basis of the pulse width modulation method.
This power converter, however, has the problem that when installed in an electric railcar, a high voltage may be produced due to a power cut or interruption which is unavoidable in the electric railcar, thereby causing destruction of and/or damage to the converter.